Electric current rectifier



July 31, 1934. RUFF 1,968,571

ELECTRIC CURRENT RECTIFIER Original Filed Nov. 11, 1932 a l \V II, a/sMurH W A A WW 2 BLUE rowan/v 0x10:

2 rem/ears SUFFURT/IVG lay/57 Inventor: Emil Rupp,

Hi5 AttOPne H Patented July 31, 1934 ELECTRIC CURRENT RECTIFIER Emil Rupp, Berlin-Frolmau, Germany, assignoi' to General Electric Company, a corporation of New York Original application November 11, 1932, Serial Divided and this application July 12, 1933, Serial No. 680,106. Renewed May 24, 1934. In Germany October 14, 1931 Claims.

- fiers of the dry plate or contact type, particularly to rectifiers of this type comprising metallic elements having an active layer formed thereon constituted by an oxide of the metallic element, and has for its principal object the provision of a rectifier of high efliciency in which the active layer is constituted by a tungsten oxide formed on a tungsten element.

I have found that the blue tungsten oxide which may be formed on tungsten metal at high temperatures possesses a high rectifying eflfect. In accordance with the invention disclosed in the aforesaid application Serial No. 637,355, such a rectifying substance is used in the making of dry rectifiers. The present invention is an improvement upon rectiflers of this kind, as will be more fully explained hereinafter.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a cross-sectional view of a rectifier of the dry plate or contact type in accordance with my invention, and Figs. 2 and 3 are cross-sectional views of modifications of the invention.

In Fig. 1 the rectifier unit of the dry plate type comprises a tungsten element or plate 1, having thereon an active layer 2 of blue tungsten oxide, and a conductive element or plate 3 in contact with the oxide layer. In the present embodiment of my invention the latter element or plate 3 is formed of bismuth.

In Fig. 2 the construction of the rectifier unit is substantially the same as that illustrated in Fig. 1 except that in Fig. 2 the bismuth element 3, in contact with the active blue tungsten oxide layer 2, is in the form of a thin layer on a supporting sheet 4 of any other suitable material.

In Fig. 3 the tungsten element 1 is in the form of a thin layer on a supporting sheet 5 of suitable material.

The method of making the tungsten oxide rectiher in accordance with my invention consists in heating blank tungsten at temperatures of 800 to 1200 C. in an oxygen-containing atmosphere for a certain time. The blue tungsten oxide which is formed in this case has (in contrast to the yellow tungsten oxide) a very pronounced rectifier effect. Unlike other rectifier substances, this substance has a very slight internal resistance, and the rectified currents are therefore very high.

Following is a description of a few of the special methods which I have found suitable for the production of the blue tungsten-oxide layer; 1. Blank tungsten in sheet form may be heated in air at 950 C. and for a few minutes (three to five for example), after which the tungsten is quenched in water. The quenching makes it pos-, sible to obtain the blue layer alone, without the yellow oxide. The quenching itself can take place in1 heated water, or in heated as well as in cold 01 I 2. Blank tungsten in sheet form may be heated as in case 1 above, in a stream of nitrogen and in a carbon-dioxide stream, after which it may be cooled in a stream of carbon-dioxide.

3. Blank tungsten in sheet form may be heated in oxygen at a reduced pressure, after which it is quenched.

4. After undergoing any one of the processes described under cases 1 to 3 above, the blue layer may be. tempered or treated at 300 to 600 C. in an atmosphere which contains a slight amount of oxygen, for instance carbon dioxide.

It is to be noted that the tungsten sheets may be formed in any suitable shape; for example, the sheets may be cut into rings.

When making rectifiers in accordance with my invention the parent metal sheet of oxide-coated tungsten serves as one electrode and the other electrode may be made of any other metal. In the aforesaid parent application Serial No. 637,355, it is stated that lead and zinc are quite appropriate for the latter purpose since they may be sprayed on to the oxide-coated tungsten sheet, and that the metal deposit constituting this other electrode may be also of electrolytic nature.

' I have found, however, that his preferable in certain cases in order to ensure, with more certainty, long life for the dry rectifier that it is of advantage to employ silver and bismuth as material for the other, or cooperating electrodes. For this purpose sheet silver, or sheet bismuth 9 as shown in Figs. 1 and 3, or bismuth which is applied to a supporting sheet of other metal in a thin coating, as shown in Fig. 2, is given a high polish and appliedby pressure to the tungsten oxide layer. The use of bismuth as a. contact metal, or metal for the cooperating electrode,

offers, furthermore, the advantage that the purpose, so that a smaller number of cells is re. no

quired ior the purpose of charging storage batteries or for analogous uses In order to prevent a further oxidation of the blue tungsten layer, reducing media may be used such as' lead oxide and graphite.

Instead oi using solid tungsten sheets, another metal may be employed as a supporting sheet. For example nickel sheets may be employed which may be plated with tungsten as shown in Fig. 3, the tungsten layer then being oxidized to form the active layer thereon.

It is to be noted that the rectifying layer exhibits also a photo-electric sensitivity and may be used as a back-wall as well as a Iront-wall" photocell.

What I claim as new and desire to secure by Letters Patent oi the United States, is:

1. A dry plate rectifier comprising a tungsten element having thereon a layer of blue tungsten oxide, and a bismuth element in contact with said oxide layer.

2. A dry plate rectifier comprising a tungsten element having thereon a layer 01' blue tungsten oxide, a layer of bismuth in contact with said oxide layer, and a supporting conductive element for said bismuth layer.

3. A dry plate rectifier comprising a tungsten element, a supporting element oi! another metal for said tungsten element, a layer or blue tungsten oxide on said tungsten element, and a bismuth element in contact with said oxide layer.

4. The process of forming a dry rectifier comprising a tungsten element having a layer of blue tungsten oxide thereon which includes applying a layer of bismuth to said tungsten oxide ayer.

5. The process of forming a dry rectifier comprising a supporting metal sheet and a tungsten sheet having a layer of blue tungsten oxide thereon which includes applying a layer 01 bismuth to said supporting sheet, and applying said bismuth coated sheet to said tungsten oxide layer.

EMIL RUPP. 

